Single-boom derricks



July 9, 1963 T. R. HALL 3,096,886

SINGLE-Boom DERRICKS Filed April 7, 1960 5 Sheets-Sheet l THOMAS R. HALLwww July 9, 1963 T. R. HA| 3,096,886

SINGLE-BOOM DERRICKS Filed April 7, 1960 5 Sheets-Sheet 2 #7| FIG. 3 A

I9 I la INVENToR.

THOMAS R. HALL www? July 9, 1963 T. R. HALL s1NGLEBooM DERRIcxs 3Sheets-Sheet 3 Filed April 7. 1960 6 8 G. 2 3 4 I .MWA F 2 flu 4,07/ .rWwl 5 ,il m" l l 9 7 um l l 4 a mw., 5 M., 5 il-.U 3 2 3 7 3 59 6 28 88G 3 8 a 9\ 4 3Q 47m 4&0 644 5 4 E \\\\\\\\A 2 it 9 .s I. 6 9 5 5 59 32 3l. 2 3 6 2 m an F 5/ vx 7? /AV 7 Kg Il I. M 1|\ 4 I O 7 M z/ n m e o a us w44 3 3 56 2 ML EL VA NH I. R S A M O H T 3 www ATT'Y.

United States Patent Ofilice 3,096,886 Patented July 9, 1963 3,096,886SINGLE-B001 DERRICKS Thomas R. Hall, Portland, Greg., assigner toMcCabe- Powers Body Company, Berkeley, Calif., a corporation ofCalifornia Filed Apr. 7, 1960, Ser. No. 20,769 9 Claims. (QL 212-35)This invention relates in general to certain new and useful improvementsin single-boom de-rricks and, more particularly, to single-boom derricksfor use on vehicles and similar mobile platforms.

It is the primary object of the present invention to provide asingle-boom derrick adapted for use on a vehicle and similar mobileplatforms and capable of being swung into any selected position from aforward or so-called transport position to a downwardly inclinedrearward position with respect to the vehicle.

It is another object of the present invention to provide a single-boom-derrick of the type stated wherein the boom may, at any of its extendedor elevated positions, be swung through a substantial arc with re-spectto the vehicle.

It is also an object of the present invention to provide a single boomderriclt of the type stated wherein the boom can be simultaneously movedin both the vertical and horizontal directions.

It is a further objectv of the present invention to provide ahydraulically operated swingable boom for use on a vehicle or the likewhich may be easily and conveniently moved to -a plurality of positionswhile in use.

With the above and other objects in View, my invention resides in thenovel features of form, construction, arrangement, and combination ofparts presently described and pointed out in the claims.

In the accompanying drawings-- FIG. l is a fragmentary side elevationalview of a truck employing a .horizontally and vertically swingable boomconstructed in accordance with and embodying the present invention;

FIG. 2 is a fragmentary perspective view showing the pivoting andactu-ating structure forming a part of the present invention;

FIG. 3 is `a fragmentary sectional view taken along line 3 3 of FIG. 2;

FIG. 4 is a lfragmentary perspective view of the means for pivotallyconnecting the driving cylinder to the body of the truck;

FIG. 5 is a fragmentary sectional view taken along line 5 5 of FIG. 2;

FIG. 6 is a `fragment-ary sectional view taken -along line 6-6 of FIG.5;

FIG. 7 is a fragmentary sectional view taken :along line 7-7 of FIG. 6;

FIG. 8 is a fragmentary sectional view taken along lline 8 8 of FIG. 2;

FIGS. 9 and 10 are fragmentary sectional views taken along lines 9 9`and lll-10, respectively, of FIG. l;

FIG. 11 is a fragmentary sectional view taken along line 11-11 of FIG.6; and

FIGS. 12, 13, and 14, are fragmentary sectional Views taken along lineslll- 12, 13-13, and 14-14, respectively, of FIG. 1.

Referring now in more detail and by reference characters to thedrawings, which illustrate a practical embodiment of the presentinvention, A designates ya vehicle including a chassis 1 and body 2having rear vertical walls 3 and horizontal top-walls 4. The particularvehicle A, being a so-called utility work body, contains a plurality ofdoorclosed tool compartments 5, 6, 7, 8, which are convention-al and arenot a part of the present invention. The chassis 1 extends rearwardlybeneath the walls 3 and 2 is provided with `depending pivot-brackets 9swingably supporting jacks 10 having cylinders 11 and piston rods 12,which are, in turn, provided with ground-engaging foot plates `13.

Welded or otherwise securely mounted on one of the top-walls 4 is anelongated anchor channel 14 provided centrally with a bracket 415 havinga pair of `'aligned apertures 16, 17. A sleeve 18 is rigidly secured tothe bracket 15 in alignment with the aperture 17 for purposes presentlymore fully appearing. Rigidly attached to the anchor channel 14 insubstantial -alignment with the bracket 15 and extending upwardlytherefrom is a retention clip 19 bent laterally inwardly at its: upperend in the provision of a guide ear 20. The clip 19 is strengthened byla gusset plate 21 which extends transversely between the lower portionlof the clip 19 and the lforward face of the bracket 15. The gussetplate 21 integrally includes a triangular camming-ear 22 which projects-above the bracket I15 and is laterally spaced from the ear 20` of theclip 19, as best seen in FIG. 3 .-and for purposes presently more fullyappearing.

Welded to the rearwardly presented end of the walls 3, which aredirectly adjacent to the anchor channel 14 and also extending verticallyabove the chassis 1, is an elongated U-shaped upright 23 which includesa bight 24 and a pair of spaced parallel anges 25, 26, which are, inturn, provided intermediate their upper margins 29, 30, and their lowermargins 27, 28, with aligned elongated notches 31, 32. Welded to theflanges 25, 26, of the upright 23 and flush along its upper f-ace withthe upper margins 29, 30, is a vertical bearing sleeve 33, whichprojects rearwardly beyond the rear vertical margins of the flanges 25,26. In like manner, a lower bearing sleeve 34 is welded to the flanges25, 26, in downwardly spaced relationship from, and in axial alignmentwith, the sleeve 33. A at ring-like thrust plate 35 is welded to theupper margin of the sleeve 33 `and also to the upper margins 29, 30, ofthe flanges 25, 26, the aperture 36 of the plate 35 being of the same`diametral size as the inner diametral size of the sleeves 33, 34, andbeing in alignment therewith. As will be seen vby reference to FIG. 2,the sleeves 33, 34, yare located respectively above and below thenotches 31, 32, so as to provide clearance forwardly of the centerlineof the sleeves 33, 34.

The flange 25 is provided with an additional rectangular notch 36 whichis spaced below the lower sleeve 34 and to which is welded a rectangularspanning plate 37, the spanning plate 37 extending between the flanges25, 26, in parallel relationship to the bight 24 and being welded alongopposite margins to the ilange 26, and to the inner margin 38 of thenotch 36. Welded to and extending rearwardly from the spanning plate 37is a U-shaped cover 39 which extends inwardly toward the longitudinalaxis of the vehicle A past the inner margin of the ange 25 and which isprovided with a flat blight portion 4t) which is parallel to thespanning plate 37. The spanning plate 37 and the bight 40 are providedwith `a pair o-f .aligned apertures 41, 42, the aperture 42 `on thebight 40 being partially surrounded -by `a pair of parallel rearwardlyextending ears 43, 44, one of each of -said ears being placed onopposite sides of the aperture 42 and eachv respectively being providedwith an aligned aperture 45, 46, the apertures 45, 46, being sized lforinsertion of -a conventional cotter pin 47. A conventional pulley-wheel48 is inserted between the spanning plate 37 `and the bight 40 of thecover 39 and is rotatably held therebetween by a bearing 49 |which isymounted on a pin 50, the pin 50` being `also inserted through theapertures 41, 42, and having a diamet-ral bore 51 which is aligned withthe apertures 45, 46, when the pin 50 is in operative position so as toreceive the cotter pin 47. It should be noted that the pulley-wheel 48is substantially tangent to the vertical centerline of the bearingsleeves 33, 34.

Rotatably mounted in the sleeves 33, 34, is a vertical tubular post orshaft 52 provided at its upper end with a horizontal cap-plate 53 havinga downwardly presented flat face 54 which bears against the uppersurface of the thiust plate 35. Welded on the outer periphery of theshaft 52 and extending radially outwardly therefrom in spaced parallelrelationship are a pair of aligned ears 55, 56, respectively, providedwith aligned apertures 57, 58, the centerline of which is perpendicularto, and in rearwardly spaced relationship from, the centerline of theshaft 52. The ears 55, 56, are located on the cylindrical shaft 53 insuch position that as the rotating column 52 rotates within the sleeves33, 34, the ears 55, 56, enter the notches 31, 32, in the flanges 25,26, thereby providing sufficient clearance to permit at least 180 ofrotation for the shaft 52. The cap-plate 53 is annular and includes alaterally extending horizontal arm 59 provided at its outer end with abore 60. Welded to and extending upwardly from the cap-plate 53 arespaced parallel inclined ears 61, `62, the ear 62 and the arm 59 beingmutually reinforced by a gusset plate 63, which extends verticallytherebetween. It should be noted that the anchor channel 14 is attachedto the upright 123 in such manner that in the area of attachment noportion of the anchor channel 14 extends above the upper margins 29, 30,of the upright 23, whereby to provide rotational freedom for therotating shaft 52.

Preferably, though not necessarily, the under face 54 of the cap-plate53 is lined with a split thrust washer 64 held in place by drive pins65, whereby to reduce the friction between the cap-plate 53 and thelthrust plate 35. The shaft 52 extends slightly below the sleeve 34, andis provided on such downwardly extended end with a removable retainerplate 66 which is annularly larger than the shaft 52 and, therefore,prevents the shaft 52 from sliding upwardly out of journaled engagementwithin the sleeves 33, 34.

Rockably secured to the radially extending arm 59 of the shaft 52 bymeans of a pin 67 mounted in the bore 60 is a double acting hydrauliccylinder or so-called hydraulic ram 68 having a piston rod 69 slidablymovable therein and being adapted, upon appropriatey application ofhydraulic fluid, to move in either direction within the cylinder 68. Thehydraulic cylinder 68 is conventional and it is, therefore, suflicientfor present purposes to state merely the function of the hydrauliccylinder and the fact that it is provided with conventional valve andconduit means for connecting the chamber within the cylinder on eitherside of the piston to a source of hydraulic fluid under pressure. Thepiston rod 69 extends outwardly from the cylinder 68 and is provided onits outer end with a collar 70 having a transverse bore 71 for receivinga pin 71 by which it is operatively secured in the bracket 15, the pin71 being disposed at its upper and lower ends in the apertures 16, 17.It should be noted that the hydraulic cylinder 68 is placed on top ofthe arm 59, so that, as the piston rod 69V is extended and retractedwithin the hydraulicV cylinder 68, the shaft 52 will rotate about itsvertical axis or centerline.

Disposed between the inclined ears 61, 62, of the shaft 52, andswingably supported therefrom, is a derrick leg 72 having a main body 73preferably comprising a pair of spaced lateral flanges 74, 75,integrally connected by a bight 76 and a spaced parallel transverse web77 in the formation of a tubular channel 78 of internal squarecross-section. As will be seen by reference to FlG. 2, the flanges '74,75, extend outwardly beyond the web 77 and are provided, approximatelymidway between the ends of the leg 72, with aligned apertures 79, 79. Atthe lower end 80 of the. derrick leg 72, the anges 74, 75, are providedwith a second set of aligned apertures 81, 82, for receiving a pin 83,by which the derrick leg 72 ispivo'lally connected between the ears 61,62. Con- 4 ventional washers 84, 85, are interposed between the ears 61,62, and the flanges 74, 7.5,-` of the derrick leg 72, and a pulley-wheel86 and a tubular bearing sleeve 87 are operatively mounted on the pin 83between the flanges 74, 75, and held in spaced relationship therefrom byconventional spacers 88, 89. lt should be noted that the pulleywheel 86is substantially tangent to the vertical centerline of the bearingsleeves 33, 34, and shaft 52. lt should be noted that the bight 76 andweb 77 are each provided'v with centrally located notches 90, 91,whereby to provide: free rotation of the pulleywheel 86. A

Disposed within the tubular channel 78 is a secondl double-actinghydraulic motor or so-called hydraulic rant 92 secured at its inner endto the derrick leg 72 by a transverse pin 93 extending through apertures94, 95, in the anges 74, 75. The hydraulic motor 92 includes aconventional cylinder 96 which projects beyond the derrick leg 72 and isprovided with a conventional piston rod 97, which is, in turn, providedat its outer end with a litting 98 having an axially projecting ear 99with a transverse bore 100 therein for receiving a pintle 101 by whichthe piston rod 97 is operatively connected to an elongated boom 102.

The boom 102 extends upwardly and downwardly from the pintle 101 and ispivotally connected at its lower end to the upper end of a link 103which is in turn, pivotally mounted at its lower end upon a horizontalpintle 104 operatively mounted in the ears 55, 56. Adjacent its upperend, the link 103 is provided with upwardly projecting ears 105, 106,for accommodating a horizontal pintle 107, which is pivotally engaged inthe lower end of a crosslink 108, the latter being also pivotallyconnected at its upper end upon a pintle 109 mounted in the apertures79, 79, of the flanges 74, 75.

At its upper end, the boom 102 is conventionally provided with a sheaveblock 110 consisting of spaced parallel plates 111, 112, which support apintle 113 and pulleywheel 114 around which a winch cable 115 istrained.

ln use, the parts are operatively connected as described and the boomassembly is transported on top of the vehicle A in the retractedposition wherein the boom 102 and derrick leg 72, with the piston rod 97fully retracted, are located in forwardly extended substantiallyhorizontal position over the body 2. In this position, the derrick leg72 will be held by the clip 19, which serves to prevent the boomassembly from inadvertently swinging tothe side during transport. Toextend the boom assembly and put itin the operative position, hydraulicfluid is applied to the cylinder 92, whereupon the derrick leg willpivot upwardly about the pin 83 and the boom 102 through theinterconnecting links 103 and 108 will swing rearwardly and upwardlyalong an arcuate path. When the piston rod 9'7 is in the fully extendedposition, the boom 102 will extend rearwardly from the vehicle body 2with the sheave block 110 near theV ground, whereupon the cable 115 maybe routed about the pulley-wheel 86 down through the tubular shaft 52and around the pulley-wheel 48. One end of the cable 115 isconventionally attached to a load to be hoisted and the other end of thecable 115 is wound upon a conventional winch (not shown) After the boom102 and derrick leg 72 have been elevated above the upper limits of theclip 19, the Afirst hydraulic cylinder 68 may be operated by theapplication of hydraulic fluid to cause the shaft 52 to rotate about itsvertical axis or centerline within the limits defined by the forwardmostmargins of the notches 31, 32. It is to be noted that two hydrauliccylinders or motors 68, 92, are independent of each other and may beindividually or conjointly operated.

Toplace the boom assembly in the transport position, it is merelynecessary to bring the shaft 52 in proper position by operation of thehydraulic cylinder or motor 68, and the hydraulic motor 92 may beoperated to cause the piston rod 97 to retract therein and thereby swingthe boom 102 and the derrick leg 73 forward over the vehicle A, untilthe derrick leg 73 rests on the gusset plate y21 between the clip 19 andthe bracket 15, substantially as shown.

It should be understood that changes and modifications in the form,construction, arrangement, and combination of the several parts of thesingle-boom derricks may be made and substituted for those herein shownand described without departing from the nature and principle of myinvention.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

l. A laterally and vertically swingable derrick cornprising la base, avertical post rotatably mounted on said base and adapted to rotatethereon about a substantially vertical axis, a laterally projectingsubstantially horizontal arm rigidly attached to the post, firsthydraulic ram means pivotally mounted at one end on the base havingrocking movement in a substantially horizontal direction and beingoperatively connected at its other end to the laterally projecting armfor rotating said post about said vertical axis, a 4derrick legpivotally mounted on the top of said post for swinging movement up anddown about a substantially horizontal axis located about the upper endof the post and in an arc Iacross the top of the post from aninoperative position to an operative position, a boom, a secondhydraulic ram means securely mounted in said derrick leg and having anextensible element adapted to extend outwardly from the swinging end ofthe derrick leg upon application of iluid pressure to the secondhydraulic ram means, said extensible element being pivotally connectedat its outer end to said boom for swinging movement about asubstantially horizontal axis, first link means pivotally connected atits outer end to said boom and being connected at its inner end to saidpost in downwardly spaced vertical relation with respect to said derrickleg, second link means pivotally connected to the first link means andthe yderrick leg so that, as said extensible element is extended, saidderrick leg will simultaneously swing up and down together with respectto said post.

2. A laterally swingable derrick for use with a truck having a rearplatform provided with a compartment including a rear wall and a topwall, said derrick comprising a channel having a pair of spaced parallelwalls and being rigidly secured to said rear wall, an anchor platesecured to said top Wall and said channel, a pair of aligned sleevesrigidly secured in spaced ver-tical relation between the parallel wallsof said channel, the upper sleeve being in ilushwise alignment with theupper end of said channel, a cylindrical post having a flange on itsupper end rotatably mounted in said aligned sleeves and having an armextending radially outwardly therefrom, said post also being providedwith a first pair of spaced parallel ears at its upper end and having asecond pair `of spaced parallel ears extending radially outwardly'therefrom intermediate its ends between the sleeves, a derrick legmounted on one end tto said post between said first pair of ears forpivotal movement about a horizontal axis, a iirst hydraulic cylindermounted in said derrick leg and having a movable piston rod extendingoutwardly therefrom, said first cylinder being adapted to cause saidpiston rod to extend and retract upon selected application of hydraulicpower from an external source, `said piston rod being extendable fromthe swinging end of the derrick leg, a first link pivotally mounted atone end to said second pair of ears, a boom pivotally connected at oneend to the first link land also being connected to the piston rod at apoint substantially near the other end of said boom, a second linkpivotally connected at one end to fthe first link and also beingpivotally connected to the derrick leg, whereby as the piston isextended from the first cylinder means, the first link pivots in thesecond pair of ears and the derrick leg pivots in the rst pair of ears,land the boom is moved vertically, and a second cylinder also having anextensible piston rod and being connected at opposite ends to said armand said anchor plate for forced rotation of the post about a verticalaxis in said sleeves.

3. The derrick of claim 2 wherein the end of the piston of the secondcylinder is pivotally connected to the anchor plate and the opposing endof lthe cylinder is pivotally connected to the arm on said post.

4. The derrick of claim 2 wherein the axes on the first link about whichthe boom and the second pair of ears are pivoted are coplaniar.

5. The derrick of claim 2 wherein the two axes on the first link aboutwhich said rst link is respectively pivoted to the boom and the secondpair of ears define a plane, and the axis of pivotal connection betweenthe first link and second link is offset from said plane and parallelthereto.

6. The derrick of claim 2 wherein the end of the piston rod on the firstcylinder and the axis about which the derrick leg pivots on the verticalpost define a plane, and the axis about which the second link pivotswith respect -to said derrick leg is parallel to and offset from saidplane.

7. The apparatus of claim 2 wherein a sheave block is operativelymounrted on the end of the boom, a first pulleywheel is operativelymounted between the first pair of spaced ears, 1a second pulley-wheel isoperatively mounted on said channel beneath the first pulley-wheel, anda cable is trained over the sheave block and the first and secondpulley-wheels and is yoperatively wound on a remote winch, said firstand second pulley-wheels being so located that the cable is routedcoaxially with respect to the vertical axis of rotation for the derrick,whereby when a load is placed on the cable and the derrick is rotatedhorizontally, the cable remains substantially stationary and inoperative connection with respect to the pulley-wheels.

8. A laterally and vertically swinging derrick for use with a vehicle orsimilar portable platform, said derrick comprising a post operativelymounted upon the vehicle for rotation about a substantially verticalaxis, a laterally projecting substantially horizontal arm rigidlyattached to salid post, a first hydraulic ram having one end pivotallymounted on the vehicle and having rocking movement in a substantiallyhorizontal plane adjacent to the upper end of the post, the other end ofsaid first hydraulic ram being pivotally attached directly to saidlaterally projecting arm for rotating said post about said verticalaxis, a first derrick frame element operatively connected at one end tothe upper end of the post so as to swing in an arc across the top of thepost from transport position to operative position, a second hydraulicram operatively mounted on the first frame-element and having anextensible element adapted for movement lengthwise with respect to thefirst frame element, said extensible element having a pivot-formingmember projecting outwardly from the first frame-element, a secondderrick frameelement pivotally attached inwardly from its outer end tosaid pivot-forming member and being operatively connected at its innerend to the outer end of a rocking link which is pivotally connected atits other end to the post in downwardly spaced relation to the firstframe-element, and a transverse link pivotally connected at its oppositeends to the rst frame-element and the rocking link respectively wherebyto cause the two frame-elements and the rocking link to swing in unison.

9. A laterally and vertically swinging derrick for use with a vehicle orsimilar portable platform, said derrick comprising a post operativelymounted upon the vehicle for rotation about a substantially `verticalaxis, a laterally projecting substantially horizontal arm rigidlyattached to said post, a first hydraulic ram pivotally mounted at oneend on the vehicle and having rocking movement in a substantiallyhorizontal plane adjacent to the upper end of the post, the other end ofsaid first hydraulic ram being pivotally attached directly to saidlaterally projecting arm for rotating said post about said verticalaxis, a first derrick leg pivotally mounted upon the upper end of thepost for vertically swinging movement about a horizontal aXis from atransport position over the vhicle to an operative position outwardly inthe clear beyond the vehicle, a second hydraulic ram operatively mountedon the rst leg and having an extensible element adapted for movementlengthwise with respect to the first leg, said extensible element havinga iirst pivot located outwardly from the first leg, a second derrick legpivotally attached inwardly from its outer end to said first pivot, saidfirst leg having a second pivot located intermediate the first pivot andsaid horizontal aXis around which the rst leg swings, said secondpivot'also being located substantially above a plane between the firstpivot and said horizontal axis when the first leg is in transportposition, said second leg when in transport position extendinglengthwise along the rst leg above the second pivot and projectingoutwardly at its `inner end beyond Vthe post with respect to the rstleg, the second lleg being operatively connected at said inner end tothe upper end of a rocking link which is Vpivotally connectedatits'other end to the post in downwardly spaced relation to the firstleg, and a transverse link pivotally connected at itsopposite ends tothe second pivot and the rocking link respectively whereby to cause thetwo legs and the rockingglink to swing in unison from transport positionto operative lposition.

References Cited iri the file of this patent UNITED STATES PATENTS

1. A LATERALLY AND VERTICALLY SWINGABLE DERRICK COMPRISING A BASE, AVERTICAL POST ROTATABLY MOUNTED ON SAID BASE AND ADAPTED TO ROTATETHEREON ABOUT A SUBSTANTIALLY VERTICAL AXIS, A LATERALLY PROJECTINGSUBSTANTIALLY HORIZONTAL ARM RIGIDLY ATTACHED TO THE POST, FIRSTHYDRAULIC RAM MEANS PIVOTALLY MOUNTED AT ONE END ON THE BASE HAVINGROCKING MOVEMENT IN A SUBSTANTIALLY HORIZONTAL DIRECTION AND BEINGOPERATIVELY CONNECTED AT ITS OTHER END TO THE LATERALLY PROJECTING ARMFOR ROTATING SAID POST ABOUT SAID VERTICAL AXIS, A DERRICK LEG PIVOTALLYMOUNTED ON THE TOP OF SAID POST FOR SWINGING MOVEMENT UP AND DOWN ABOUTA SUBSTANTIALLY HORIZONTAL AXIS LOCATED ABOUT THE UPPER END OF THE POSTAND IN AN ARC ACROSS THE TOP OF THE POST FROM AN INOPERATIVE POSITION TOAN OPERATIVE POSITION, A BOOM, A SECOND HYDRAULIC RAM MEANS SECURELYMOUNTED IN SAID DERRICK LEG AND HAVING AN EXTENSIBLE ELEMENT ADAPTED TOEXTEND OUTWARDLY FROM THE SWINGING END OF THE DERRICK LEG UPONAPPLICATION OF FLUID PRESSURE TO THE SECOND HYDRAULIC RAM MEANS, SAIDEXTENSIBLE ELEMENT BEING PIVOTALLY CONNECTED AT ITS OUTER END TO SAIDBOOM FOR SWINGING MOVEMENT ABOUT A SUBSTANTIALLY HORIZONTAL AXIS, FIRSTLINK MEANS PIVOTALLY CONNECTED AT ITS OUTER END TO SAID BOOM AND BEINGCONNECTED AT ITS INNER END TO SAID POST IN DOWNWARDLY SPACED VERTICALRELATION WITH RESPECT TO SAID DERRICK LEG, SECOND LINK MEANS PIVOTALLYCONNECTED TO THE FIRST LINK MEANS AND THE DERRICK LEG SO THAT, AS SAIDEXTENSIBLE ELEMENT IS EXTENDED, SAID DERRICK LEG WILL SIMULTANEOUSLYSWING UP AND DOWN TOGETHER WITH RESPECT TO SAID POST.